
/*
//K个一组翻转链表
public ListNode reverseKGroup(ListNode head, int k) {
        ListNode dummy = new ListNode(0);
        dummy.next = head;

        ListNode pre = dummy;
        ListNode end = dummy;

        while (end.next != null) {
        for (int i = 0; i < k && end != null; i++) end = end.next;
        if (end == null) break;
        ListNode start = pre.next;
        ListNode next = end.next;
        end.next = null;
        pre.next = reverse(start);
        start.next = next;
        pre = start;

        end = pre;
        }
        return dummy.next;
        }

private ListNode reverse(ListNode head) {
        ListNode pre = null;
        ListNode curr = head;
        while (curr != null) {
        ListNode next = curr.next;
        curr.next = pre;
        pre = curr;
        curr = next;
        }
        return pre;
        }*/
